Variable displacement compressor

Abstract

A modulating system for a rotary hermetic compressor is provided with a valve operable by a force varying with the difference in pressure between the suction and discharge pressure for allowing a portion of the refrigerant gas being compressed to travel from the compression side of the roller to the suction side of the roller when the design peak load of the compressor is exceeded.

What is claimed is: 
     
       1. A hermetic rotary refrigerant compressor for use in a refrigeration system including refrigerant condensing means for condensing high pressure gaseous refrigerant from said compressor, an expansion device, and evaporator means wherein liquid refrigerant vaporizes and absorbs heat of evaporization comprising: a hermetic casing adapted to contain a high pressure refrigerant gas;   a rotary compressor positioned in said casing and comprising means including a cylindrical wall member and upper and lower end plates forming the axial walls of an annular compression cylinder, spaced suction and discharge ports communicating with said cylinder;   means connecting said suction port to the evaporator;   means connecting said discharge port through a discharge valve to said casing;   a rotor extending axially between said plates being eccentrically rotatable within said cylinder with the peripheral surface of said rotor arranged to move progressively into sealing relation with successive portions of said cylindrical wall of said annular cylinder to divide said cylinder between a suction side and a compression side;   a motor having a shaft thereon for driving said rotor within said cylinder;   a radially disposed vane slidably maintained in a slot in said wall member between said ports being biased against said rotor to divide said cylinder into low and high pressure sides within said cylinder;   pressure relief means including channel means formed in one of said end plates, said channel being arranged and dimensioned so that a portion thereof is exposed to said cylinder to form a passageway on said low pressure side of said cylinder;   valve means including a valve in said channel and valve actuating means responsive to discharged refrigerant pressure in said casing being operable for moving said valve from a sealing position flush with the axial wall of said cylinder to an open position in said channel by a force varying with the difference in pressure between the suction and discharge pressures for allowing a portion of said refrigerant being compressed in said cylinder by said rotor to flow through said passageway from the compression side of the peripheral surface of said rotor to the suction side of the peripheral surface of said rotor when the pressure of refrigerant in said casing is greater than a predetermined pressure so that refrigerant pressure at said discharge port is maintained within said predetermined pressure.   
     
     
       2. The hermetic rotary compressor recited in claim 1 wherein in its closed position the wall of said valve facing said cylinder is in a plane defined by the axial wall of said one of said end plates. 
     
     
       3. The hermetic rotary compressor recited in claim 2 wherein said valve in its open position departs the plane from a position adjacent said valve actuating means and progressively converges to a point in the plane that varies in distance from said valve actuating means relative to the pressure in said casing. 
     
     
       4. The hermetic rotary compressor recited in claim 1 wherein said channel is substantially circular extending circumferentially about said cylinder. 
     
     
       5. The hermetic rotary compressor recited in claim 4 wherein said valve means is circular and dimensioned radially to seal against the circumferential walls of said channel. 
     
     
       6. The hermetic rotary compressor recited in claim 1 wherein said valve actuating means further includes a plurality of valve positioning means slidably arranged in said plate each having one end thereof engaging the upper surface of said valve and the other end thereof being exposed to high pressure refrigerant gas in said casing for biasing said valve means in a position flush with the plate wall exposed to said cylinder to seal said passageway from said cylinder. 
     
     
       7. The hermetic rotary compressor recited in claim 6 wherein said valve actuating means further includes a valve operating means arranged in said cylindrical wall member having a portion being larger in area exposed to said casing pressure than said positioning means so that when pressure of said refrigerant gas in said casing is greater than a predetermined amount, said valve operating means causes said valve member to move from its sealing position. 
     
     
       8. The hermetic rotary compressor recited in claim 7 wherein said valve operating means further includes biasing means operable for allowing said valve to remain in said sealing position when the pressure in said casing is within a predetermined range and for yielding when the pressure in said casing is greater than a predetermined pressure to allow said valve operating means to cause said valve to move from its sealing position. 
     
     
       9. The hermetic rotary compressor recited in claim 8 wherein said passageway is in communication with said cylinder substantially between the vane and a point diametrically opposite thereof. 
     
     
       10. The hermetic rotary compressor recited in claim 8 wherein in its closed position the wall of said valve facing said cylinder is in a plane defined by the axial wall of said one of said end plates. 
     
     
       11. The hermetic rotary compressor recited in claim 10 wherein said valve in its open position departs from a position adjacent said vane and progressively converges to a point in the plane that varies in distance from the vane relative to the pressure in said casing.